Blade retention device



S. L. LEAVITT BLADE RETENTION DEVICE July 31, 1962 Filed March 14, 1960 2 Sheets-Sheet 1 IN VEN TOR. 6771/746741 W77 1962 s. L. LEAVITT BLADE RETENTION DEVICE 2 Sheets-Shet 2 Filed March 14, 1960 /FFAA INVHVTOR.

JmME/LJMV/I'I' BY Unite drama 3,047,268 BLADE RETENTIQN DEVKIE Stanley L. Leavitt, Bristol, Coma, assignor to the United States of America as represented by the Secretary of the Air Force Filed Mar. 14, 1960, Ser. No. 15,002 2 Claims. (Cl. 253-77) This invention relates generally to a blade retention device suitable for securing rotor blades in the compressor or turbine stages of a gas turbine engine, and more particularly to one which eliminates the utilization of tablocks or rivets customarily used to retain blades in engines.

In engines of this type there may be several compression stages driven by several stages of turbines, each stage consisting of one or more discs upon the periphery of which are mounted a plurality of blades. The blades are not made integral with the discs and it is desirable to have some means for securing the blades to the discs which will hold them firmly in place and at the same time allow convenient removal and replacement.

There are many retention devices for securing compression or turbine blades on discs, such as tabs of metal bent to secure the blade, wedges or rivets which hold the blades in place but which are difficult of removal and, furthermore, cause projections in the air stream causing unwanted friction or drag.

It is an object of this invention to provide a blade retention device which will make removal and replacement of blades easy and convenient.

It is a further object of this invention to provide a blade retention device which holds the blades securely in place without projections.

It is a further object to provide a blade retention device which will allow a larger and stronger root section of the blade than is customary with tablock securing and at the same time decrease the dead rim volume of the disc.

A still further object is to provide a blade with a wider and stronger foot which will enable simpler disc construction and make unnecessary the use of heavy spacer platforms.

It is a further object to provide a combination windage cover and retainer plate which carries integral seal supports.

The above and still other objects, advantages and features of my invention will become apparent upon consideration of the following detailed description thereof, especially when taken in conjunction with the following drawings in which:

FIGURE 1 is a perspective view of part of a rotor blade showing the construction of the foot;

FIGURE 2 is a perspective view, partly in section, showing part of a disc and rotor blade assembly; and

FIGURE 3 is a sectional view showing the novel rotor blade mounting in conjunction with a portion of a multi-stage compressor.

In FIGURES 1 and 2, a rotor blade unit is shown with a portion of the root 12 formed to fit in a generally dove-tailed slot 14 in the rim 16 of a disc 20. The root portion includes a platform 22 from which blade portion 11 protrudes. A leading edge 18 of the platform 22 of the rotor blade unit 10 fits against a shoulder 24 cut on the rim 16 of the disc 20. This structure prevents axial movement of the rotor blade unit 10 in one axial direction. The root of the rotor blade unit 10 is held in the slot 14 by a retainer plate 28,

the edge of which fits in a notch 26 cut in lower portion of the rear edge of the rotor blade platform 22. The retainer plate 28 is held firmly in place by a combination windage cover and seal support 30.

As can best be seen in FIGURE 3, the retaining plate 28 is held firmly against the notch 26 of the foot of blade unit 10 by the strut, or bracing action of the windage cover 30 which abuts the forward face of a disc 20 of the next stage. The windage cover 30 carries a seal support 32 which meets with a sealing surface 36 attached to stator blade 34. The retainer plate 28 also carries a seal support 33 which meets a similar sealing surface 36 on the stator blade 34.

As can be seen in FIGURES 1 and 2, the platform 22 of the blade 10 is of a width to meet the platform of the adjacent blade when the said blades are inserted in the slots 14 in the rim 16 of the discs 20, thus eliminating the necessity of a spacer plate between blades and strengthening the seat of the blade 10.

Not only does this construction give a stronger blade seat and more resistance to axial and radial movement of the blade on the disc, but it makes the machining of the blade and the disc much simpler and easier. The rim of the disc can be much lighter, with this simplified construction, as well as easier to form.

Although this invention has been described with reference to a particular embodiment, it will be understood that the invention is capable of a variety of alternative embodiments within the spirit and scope of the appended claims.

I claim:

1. For a gas turbine engine, the combination with a turbine rotor comprising a rotor disc, a series of axial dovetail slots extending through the outer circumference of said rotor disc, a series of rotor blades, each of said blades having a blade portion of airfoil cross-section, a root section secured to said blade portion, said root section comprising a platform and a dovetail of a size to be received by said dovetail slots, said platform being located between said blade portion and said dovetail, a shoulder on the outer circumference of said rotor disc forming circumferential segments separated by said dovetail slots in said rotor disc, said platforms having cutout portions equal to the depth of said shoulder segments such that insertion of said root section in said slots provides abutment of said platform against said shoulder segments to limit axial movement of said rotor blades in one direction, a notch in said platform opposite said cutout portions and on the side of said platform adjacent said dovetail, and an annular plate in engagement with said notch for limiting movement of said rotor blades in the other of said axial directions.

2. For a gas turbine engine as defined in claim 1 the combination including a windage cover in engagement with said disc, said windage cover providing a support for said plate.

References Cited in the file of this patent UNITED STATES PATENTS 2,683,583 Huebner et al. July 13, 1954 2,686,656 Abild Aug. 17, 1954 2,751,189 Ledwith June 19, 1956 2,828,942 McCullough Apr. 1, 1958 2,928,650 Hooker et al. Mar. 15, 1960 2,928,651 Turnbull Mar. 15, 1960 2,972,470 McCormick Feb. 21, 1961 FOREIGN PATENTS 670,665 Great Britain Apr. 23, 1952 

